<template>
  <!-- 只有在总页数大于1的时候才显示 -->
  <div class="pager-container" v-if="pageNumber > 1">
    <a @click="handleClick(1)" :class="{ disabled: current === 1 }">|&lt;&lt;</a>
    <a @click="handleClick(current - 1)" :class="{ disabled: current === 1 }">&lt;&lt;</a>

    <a @click="handleClick(n)" v-for="(n, i) in numbers" :key="i" :class="{ active: n === current }">{{ n }}</a>

    <a @click="handleClick(current + 1)" :class="{ disabled: current === pageNumber }">&gt;&gt;</a>
    <a @click="handleClick(pageNumber)" :class="{ disabled: current === pageNumber }">&gt;&gt;|</a>
  </div>
</template>

<script>
export default {
  props: {
    // 当前页
    current: {
      type: Number,
      default: 1
    },
    // 数据总条数
    total: {
      type: Number,
      default: 0
    },
    // 每页显示的数据条数
    limit: {
      type: Number,
      default: 10
    },
    // 可见的页码数量
    visibleNumber: {
      type: Number,
      default: 10
    }
  },
  computed: {
    // 总页数
    pageNumber() {
      return Math.ceil(this.total / this.limit)
    },
    // 得到显示的最小/最大数字
    visibleMin() {
      let min = this.current - Math.floor(this.visibleNumber / 2)
      if (min < 1) {
        min = 1
      }
      return min
    },
    visibleMax() {
      let max = this.current + this.visibleNumber - 1
      if (max > this.pageNumber) {
        max = this.pageNumber
      }
      return max
    },
    numbers() {
      let nums = []
      for (let i = this.visibleMin; i <= this.visibleMax; i++) {
        nums.push(i)
      }
      return nums
    }
  },
  methods: {
    handleClick(newPage) {
      if (newPage < 1) {
        newPage = 1
      }
      if (newPage > this.pageNumber) {
        newPage = this.pageNumber
      }
      if (newPage === this.current) {
        return
      }
      // 抛出事件
      this.$emit('pageChange', newPage)
    }
  }
}
</script>

<style lang="less" scoped>
@import '~@/styles/var.less';
.pager-container {
  display: flex;
  justify-content: center;
  margin: 20px 0;
  a {
    color: @primary;
    margin: 0 6px;
    cursor: pointer;
    &.disabled {
      color: @lightWords;
      cursor: not-allowed;
    }
    &.active {
      color: @words;
      font-weight: bold;
      cursor: text;
    }
  }
}
</style>
